Abstract [en]

OBJECTIVES: The aim of this study was to evaluate the chemokine CXCL13 and C6 antibodies separately and in combination in paired serum/cerebrospinal fluid (CSF) samples in the laboratory diagnosis of Lyme neuroborreliosis (LNB).

METHODS: A large retrospective material with paired serum/CSF samples from 261 patients with clinically suspected LNB was investigated. Patients were divided into three main diagnostic groups based on original results of CSF pleocytosis and intrathecal anti-borrelia antibodies (purified flagellum). Levels of CXCL13, albumin, total IgM and IgG in paired samples and C6 antibodies in CSF were compared across diagnostic groups.

RESULTS: A sensitivity of 99% and a specificity of 96% were achieved for CSF-Serum CXCL13 ratio. CSF-C6 antibodies performed with a sensitivity of 99% and a specificity of 88.0%. A combination of CSF-Serum CXCL13 ratio and CSF-C6 antibodies, evaluated in parallel, revealed a sensitivity of 99% and specificity of 98%.

CONCLUSIONS: This study confirms CSF-CXCL13 as a reliable marker of LNB and suggests improved diagnostic performance especially in children with possible LNB.

Abstract [en]

Lyme borreliosis (LB), the most common tick-borne disease in Europe and North America, is caused by spirochetes of the Borrelia burgdorferi sensu lato complex. The spirochetes can invade several different organs, thereby causing many different symptoms and signs. Diagnosis of LB relies on patient history, physical examination, and detection of anti-Borrelia antibodies. However, anti-Borrelia antibodies are not always detectable, and they commonly persist even after LB is successfully treated or spontaneously healed.

The aim of my work was to study diagnostic aspects on clinical cases of LB and control subjects in an area endemic to LB, with a focus on newly developed anti-Borrelia antibody tests. A total of 617 patients with symptoms and/or signs consistent with LB, as well as 255 control subjects, were studied. The diagnostic panel included the following new LB tests: Immunetics Quick ELISA C6 Borrelia assay kit (C6), invariable region 6 peptide antibody assays (IR6), Liaison Borrelia CLIA (Li) and the chemokine CXCL13. Results were compared with the older Virotech Borrelia burgdorferi ELISA (VT) and with a Western blot method, the Virotech Borrelia Ecoline IgG/IgM Line Immunoblot (WB EL), when appropriate.

In general, no significant differences were noted between the C6, VT and Li tests regarding serosensitivity in various LB manifestations. However, the seropositivity rate was lower for the C6 test compared with the VT and Li tests 2–3 and 6 months after diagnosis of erythema migrans (EM), indicating normalization of antibody levels. In addition, EM patients reporting a previous LB episode had a C6 seropositivity rate similar to that of patients without a previous LB episode, and seroprevalence in healthy blood donors was lower in the C6 test than the VT and Li tests. Taken together, these results support the recommendation of the serum C6 test as a Borrelia serological test due to its ability to reflect ongoing or recent infection.

Although the majority of EM patients at presentation showed concordant serological responses to IR6 peptides representing the three main Borrelia species and the C6 peptide, there were also clinical EM cases that were C6-negative and could be detected mainly by a seroresponse to a B. burgdorferi sensu stricto-derived IR6 peptide. Thus, an antibody test combining antigens could be of value in the serodiagnosis of LB in Europe.

The serosensitivity of the C6 test in cases of Lyme neuroborreliosis (LNB) was shown to be associated with symptom duration. A serosensitivity rate of 93% was found in LNB patients ³ 12 years of age with a symptom duration of more than 30 days. Therefore, a negative C6 test in serum in such a patient argues against an LNB diagnosis.

The presence of chemokine CXCL13 in cerebrospinal fluid was confirmed to be a reliable marker of LNB. CXCL13 differentiated LNB from other conditions and also indicated a high probability of LNB in children with short symptom duration where anti-Borrelia antibodies were still lacking in the cerebrospinal fluid.

A two-tiered approach (C6 test in combination with WB EL) showed no significant improvement in specificity over the C6 test alone. However, WB EL may be useful in diagnosing suspected cases of acrodermatitis chronicum atrophicans and Lyme arthritis, usually displaying multiple IgG bands.

In conclusion, although the serodiagnosis of LB remains to be settled, this thesis provides some practical tools regarding the use and interpretation of Borrelia serology including proposed diagnostic routines.